Hey Justin,  Long reply to follow... With regards to modifying the seating compartment...  At issue is one of flotation. The uscg does not recognize air chambers as flotation and when tested, holes are specified to be drilled into any air compartments such that they completely flood for the flotation and level-flotation tests. In the eyes of the CG,  B&B is the "builder" of your boat because we manufactured the kit (i know it's weird) and so we are required to issue an HIN number